The present invention relates to an improved method and apparatus for spinning a multifilament yarn.
A method and an apparatus of the described type are known from U.S. Pat. No. 4,277,430, which discloses an apparatus wherein a bundle of filaments emerging from a spinneret is cooled by directing a transverse airflow into contact with the filaments. Downstream of the transverse airflow cooling, the cooling shaft is lengthened by a second section. In the inlet region of the lower cooling shaft, a mixture of air and water is introduced into the cooling shaft as a mistlike cooling stream which flows by means of suction in the direction of the yarn advance and to the end of the cooling zone. In this process, a greater cooling effect is realized on the filaments by the addition of a liquid. However, this prior method has the disadvantage that a considerable portion of air enters from the transverse airflow directly into the lower cooling shaft. As a result, an airflow forms that surrounds each filament. This airflow prevents liquid particles from reaching the surface of the filament.
Methods and apparatus for melt spinning yarns are also known wherein at higher yarn speeds the filaments are cooled by an air stream that flows in the cooling shaft at a high velocity, as is disclosed, for example, in EP 0 244 217 or WO 95/1540. However, such methods basically have the disadvantage that there is no intensive cooling of the filaments. These methods are suitable in particular for yarns with relatively fine deniers. In addition, the known methods lead to a distinct hot drawing that results in an orientation of the molecules within the filaments.
It is accordingly an object of the invention to further develop a method and an apparatus for melt spinning a multifilament yarn of the initially described type in such a manner that the yarn can be cooled without undergoing a substantial partial orientation.